642 
BULLETIN OF THE BUBEAU OF FISHEBIES 
In 1916 the temperature of the upper 30 meters was about the same a few 
miles off Cape Ann on October 31 (station 10399, surface 10°, 30 meters 9.18°) as it 
was on the 3d to the 16th in Passamaquoddy Bay, showing a regional difference of 
about two weeks in the autumnal schedule between the southwestern and the north- 
eastern parts of the gulf. This corresponds both to the land climate and to the 
difference in latitude. 
Our only records of autumnal temperatures for the offshore parts of the gulf 
later than the first week of September are for its western and southwestern parts, 
where serial readings were taken on November 1, 1916 (station 10401), and again 
on the 8th of the month (station 10404). In this very cold year the autumnal 
warming of the deeper layers may have lagged some weeks behind the normal; the 
inflow of water of high salinity into the bottom of the trough seems also to have been 
in smaller volume than usual. Consequently, the temperatures of 1916 can hardly 
be taken as typical for depths greater than 100 meters. 
Surface readings about 0.5° higher in the offing of Cape Ann (station 10401, 
10.6°) than near Gloucester, 0.9° warmer than off the Isles of Shoals, and 1.3° 
warmer than off Penobscot Bay on November 1 and 2 of that year show cooling 
most rapid next to the land, as might be expected. This regional difference is 
slight, however, and the deeper strata show much the same autumnal change off- 
shore as they do closer to land, with the 40 to 70 meter level warming slightly (fig. 
72) while the surface cools. At depths greater than this annual differences entirely 
overshadowed any seasonal alteration that may take place in the western side of 
the basin between August and October. 
As a result of the progressive equalization of temperature, horizontal as well as 
vertical, that takes place during the autumn, the regional variation in the temper- 
ature of the western side of the gulf was only about 1.5° to 2° at any given level 
deeper than 15 meters in the first week of November, 1916. This close approach 
to uniformity is probably typical of the season, though the precise temperature at 
any level varies slightly from year to year. 
The average temperature of the region west of the longitude of Penobscot Bay 
and north of Cape Cod is approximately as follows by the first of November in 
normal years : 
Depth 
Average 
temper- 
ature 
Aug. 15 
Average 
temper- 
ature 
Nov. 1 
Seasonal 
change 
Surface-. . __ _ 
°c. 
15. 0-18. 0 
°c. 
10.0 
°c. 
-5. 0-8. 0 
20 meters 
11.5 
9.5 
-2.0 
40 meters 
7.2 
8.9 
+ 1.6 
70 meters 
5.6 
7.0 
+ 1.4 
100 meters 
4.7 
5.0 
+.3 
No records of the subsurface temperatures have been taken on Georges Bank 
in autumn. In the shallow water of Nantucket Shoals autumnal cooling may at first 
reduce the temperature of the surface slightly below that of the bottom, the Halcyon 
having recorded surface readings of 11.6° to 12.2° on October 1, 1925, on the shoal, 
when the bottom water was 12° to 13.5° in a depth of about 25 meters (p. 1013). 
